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4 commits

Author SHA1 Message Date
Hui Xiao 75a1230ce8 Fix improper ExpectedValute::Exists() usages and disable compaction during VerifyDB() in crash test (#12933)
Summary:
**Context:**
Adding assertion `!PendingPut()&&!PendingDelete()` in `ExpectedValute::Exists()` surfaced a couple improper usages of `ExpectedValute::Exists()` in the crash test
- Commit phase of `ExpectedValue::Delete()`/`SyncDelete()`:
When we issue delete to expected value during commit phase or `SyncDelete()` (used in crash recovery verification) as below, we don't really care about the result.
d458331ee9/db_stress_tool/expected_state.cc (L73)
d458331ee9/db_stress_tool/expected_value.cc (L52)
That means, we don't really need to check for `Exists()` d458331ee9/db_stress_tool/expected_value.cc (L24-L26).
This actually gives an alternative solution to b65e29a4a9 to solve false-positive assertion violation.
- TestMultiGetXX() path: `Exists()` is called without holding the lock as required

f63428bcc7/db_stress_tool/no_batched_ops_stress.cc (L2688)
```
void MaybeAddKeyToTxnForRYW(
      ThreadState* thread, int column_family, int64_t key, Transaction* txn,
      std::unordered_map<std::string, ExpectedValue>& ryw_expected_values) {
    assert(thread);
    assert(txn);

    SharedState* const shared = thread->shared;
    assert(shared);

    if (!shared->AllowsOverwrite(key) && shared->Exists(column_family, key)) {
      // Just do read your write checks for keys that allow overwrites.
      return;
    }

    // With a 1 in 10 probability, insert the just added key in the batch
    // into the transaction. This will create an overlap with the MultiGet
    // keys and exercise some corner cases in the code
    if (thread->rand.OneIn(10)) {
```

f63428bcc7/db_stress_tool/expected_state.h (L74-L76)

The assertion also failed if db stress compaction filter was invoked before crash recovery verification (`VerifyDB()`->`VerifyOrSyncValue()`) finishes.
f63428bcc7/db_stress_tool/db_stress_compaction_filter.h (L53)
It failed because it can encounter a key with pending state when checking for `Exists()` since that key's expected state has not been sync-ed with db state in `VerifyOrSyncValue()`.
f63428bcc7/db_stress_tool/no_batched_ops_stress.cc (L2579-L2591)

**Summary:**
This PR fixes above issues by
- not checking `Exists()` in commit phase/`SyncDelete()`
- using the concurrent version of key existence check like in other read
- conditionally temporarily disabling compaction till after crash recovery verification succeeds()

And add back the assertion `!PendingPut()&&!PendingDelete()`

Pull Request resolved: https://github.com/facebook/rocksdb/pull/12933

Test Plan: Rehearsal CI

Reviewed By: cbi42

Differential Revision: D61214889

Pulled By: hx235

fbshipit-source-id: ef25ba896e64330ddf330182314981516880c3e4
2024-08-15 12:32:59 -07:00
Hui Xiao 112bf15dca Fix false-positive TestBackupRestore corruption (#12917)
Summary:
**Context:**
https://github.com/facebook/rocksdb/pull/12838 allows a write thread encountered certain injected error to release the lock and sleep before retrying write in order to reduce performance cost. This requires adding checks like [this](b26b395e0a/db_stress_tool/expected_value.cc (L29-L31)) to prevent writing to the same key from another thread.

The added check causes a false-positive failure when delete range + file ingestion + backup is used. Consider the following scenario:
(1) Issue a delete range covering some key that do not exist and a key does exist (named as k1). k1 will have "pending delete" state while the keys that does not exit will have whatever state they already have since we don't delete a key that does not exist already.
(2) After https://github.com/facebook/rocksdb/pull/12838,  `PrepareDeleteRange(... &prepared)` will return `prepared = false`. So below logic will be executed and k1's "pending delete" won't get roll-backed nor committed.
```
std::vector<PendingExpectedValue> pending_expected_values =
        shared->PrepareDeleteRange(rand_column_family, rand_key,
                                   rand_key + FLAGS_range_deletion_width,
                                   &prepared);
    if (!prepared) {
      for (PendingExpectedValue& pending_expected_value :
           pending_expected_values) {
        pending_expected_value.PermitUnclosedPendingState();
      }
      return s;
    }
```
(3) Issue an file ingestion covering k1 and another key k2. Similar to (2), we will have  `shared->PreparePut(column_family, key, &prepared)` return `prepared = false` for k1 while k2 will have a "pending put" state. So below logic will be executed and k2's "pending put" state won't get roll-backed nor committed.
```
for (int64_t key = key_base;
         s.ok() && key < shared->GetMaxKey() &&
         static_cast<int32_t>(keys.size()) < FLAGS_ingest_external_file_width;
         ++key)
      PendingExpectedValue pending_expected_value =
                shared->PreparePut(column_family, key, &prepared);
            if (!prepared) {
              pending_expected_value.PermitUnclosedPendingState();
              for (PendingExpectedValue& pev : pending_expected_values) {
                pev.PermitUnclosedPendingState();
              }
              return;
            }
}
```
(4) Issue a backup and verify on k2. Below logic decides that k2 should exist in restored DB since it has a pending write state while k2 is never ingested into the original DB as (3) returns early.
```
bool Exists() const { return PendingPut() || !IsDeleted(); }

TestBackupRestore() {
...
Status get_status = restored_db->Get(
        read_opts, restored_cf_handles[rand_column_families[i]], key,
        &restored_value);
    bool exists = thread->shared->Exists(rand_column_families[i], rand_keys[0]);
    if (get_status.ok()) {
      if (!exists && from_latest && ShouldAcquireMutexOnKey()) {
        std::ostringstream oss;
        oss << "0x" << key.ToString(true)
            << " exists in restore but not in original db";
        s = Status::Corruption(oss.str());
      }
    } else if (get_status.IsNotFound()) {
      if (exists && from_latest && ShouldAcquireMutexOnKey()) {
        std::ostringstream oss;
        oss << "0x" << key.ToString(true)
            << " exists in original db but not in restore";
        s = Status::Corruption(oss.str());
      }
    }
   ...
}
```
So we see false-positive corruption like `Failure in a backup/restore operation with: Corruption: 0x000000000000017B0000000000000073787878 exists in original db but not in restore`

A simple fix is to remove `PendingPut()` from `bool Exists() ` since it's called under a lock and should never see a pending write. However, in order for "under a lock and should never see a pending write" to be true, we need to remove the logic of releasing the lock during sleep in the write thread, which expose pending write to other thread that can call Exists() like back up thread.

The downside of holding lock during sleep is blocking other write thread of the same key to proceed cuz they need to wait for the lock. This should happen rarely as the key of a thread is selected randomly in crash test like below.

```
void StressTest::OperateDb(ThreadState* thread) {
   for (uint64_t i = 0; i < ops_per_open; i++) {
     ...
     int64_t rand_key = GenerateOneKey(thread, i);
     ...
   }
}
```

**Summary:**
- Removed the "lock release" part and related checks
- Printed recovery time if the write thread waited more than 10 seconds
- Reverted regression in testing coverage when deleting a non-existent key

Pull Request resolved: https://github.com/facebook/rocksdb/pull/12917

Test Plan:
Below command repro-ed frequently before the fix and not after.
```

./db_stress --WAL_size_limit_MB=1 --WAL_ttl_seconds=60 --acquire_snapshot_one_in=0 --adaptive_readahead=0 --adm_policy=1 --advise_random_on_open=1 --allow_concurrent_memtable_write=0 --allow_data_in_errors=True --allow_fallocate=0 --allow_setting_blob_options_dynamically=1 --async_io=0 --auto_readahead_size=1 --avoid_flush_during_recovery=0 --avoid_flush_during_shutdown=0 --avoid_unnecessary_blocking_io=0 --backup_max_size=104857600 --backup_one_in=100000 --batch_protection_bytes_per_key=0 --bgerror_resume_retry_interval=100 --blob_cache_size=8388608 --blob_compaction_readahead_size=1048576 --blob_compression_type=none --blob_file_size=1073741824 --blob_file_starting_level=1 --blob_garbage_collection_age_cutoff=0.0 --blob_garbage_collection_force_threshold=0.75 --block_align=0 --block_protection_bytes_per_key=8 --block_size=16384 --bloom_before_level=2147483647 --bloom_bits=16.216959977115277 --bottommost_compression_type=xpress --bottommost_file_compaction_delay=600 --bytes_per_sync=262144 --cache_index_and_filter_blocks=1 --cache_index_and_filter_blocks_with_high_priority=1 --cache_size=8388608 --cache_type=lru_cache --charge_compression_dictionary_building_buffer=1 --charge_file_metadata=0 --charge_filter_construction=0 --charge_table_reader=1 --check_multiget_consistency=0 --check_multiget_entity_consistency=0 --checkpoint_one_in=1000000 --checksum_type=kXXH3 --clear_column_family_one_in=0 --column_families=1 --compact_files_one_in=1000 --compact_range_one_in=0 --compaction_pri=3 --compaction_readahead_size=0 --compaction_ttl=10 --compress_format_version=2 --compressed_secondary_cache_size=8388608 --compression_checksum=0 --compression_max_dict_buffer_bytes=2097151 --compression_max_dict_bytes=16384 --compression_parallel_threads=1 --compression_type=zlib --compression_use_zstd_dict_trainer=0 --compression_zstd_max_train_bytes=0 --continuous_verification_interval=0 --daily_offpeak_time_utc=04:00-08:00 --data_block_index_type=0 --db=/dev/shm/rocksdb_test/rocksdb_crashtest_whitebox --db_write_buffer_size=0 --default_temperature=kUnknown --default_write_temperature=kWarm --delete_obsolete_files_period_micros=21600000000 --delpercent=0 --delrangepercent=5 --destroy_db_initially=0 --detect_filter_construct_corruption=1 --disable_file_deletions_one_in=10000 --disable_manual_compaction_one_in=1000000 --disable_wal=0 --dump_malloc_stats=0 --enable_blob_files=0 --enable_blob_garbage_collection=1 --enable_checksum_handoff=1 --enable_compaction_filter=1 --enable_custom_split_merge=1 --enable_do_not_compress_roles=0 --enable_index_compression=1 --enable_memtable_insert_with_hint_prefix_extractor=0 --enable_pipelined_write=1 --enable_sst_partitioner_factory=1 --enable_thread_tracking=0 --enable_write_thread_adaptive_yield=0 --error_recovery_with_no_fault_injection=1 --exclude_wal_from_write_fault_injection=1 --expected_values_dir=/dev/shm/rocksdb_test/rocksdb_crashtest_expected --fail_if_options_file_error=0 --fifo_allow_compaction=1 --file_checksum_impl=big --fill_cache=1 --flush_one_in=1000000 --format_version=2 --get_all_column_family_metadata_one_in=10000 --get_current_wal_file_one_in=0 --get_live_files_apis_one_in=1000000 --get_properties_of_all_tables_one_in=100000 --get_property_one_in=100000 --get_sorted_wal_files_one_in=0 --hard_pending_compaction_bytes_limit=2097152 --high_pri_pool_ratio=0.5 --index_block_restart_interval=1 --index_shortening=2 --index_type=0 --ingest_external_file_one_in=1000 --initial_auto_readahead_size=0 --inplace_update_support=0 --iterpercent=0 --key_len_percent_dist=1,30,69 --key_may_exist_one_in=100 --last_level_temperature=kUnknown --level_compaction_dynamic_level_bytes=0 --lock_wal_one_in=10000 --log2_keys_per_lock=10 --log_file_time_to_roll=0 --log_readahead_size=0 --long_running_snapshots=1 --low_pri_pool_ratio=0.5 --lowest_used_cache_tier=1 --manifest_preallocation_size=0 --manual_wal_flush_one_in=0 --mark_for_compaction_one_file_in=10 --max_auto_readahead_size=16384 --max_background_compactions=1 --max_bytes_for_level_base=67108864 --max_key=100000 --max_key_len=3 --max_log_file_size=1048576 --max_manifest_file_size=1073741824 --max_sequential_skip_in_iterations=16 --max_total_wal_size=0 --max_write_batch_group_size_bytes=16 --max_write_buffer_number=10 --max_write_buffer_size_to_maintain=8388608 --memtable_insert_hint_per_batch=1 --memtable_max_range_deletions=1000 --memtable_prefix_bloom_size_ratio=0.001 --memtable_protection_bytes_per_key=4 --memtable_whole_key_filtering=1 --memtablerep=skip_list --metadata_charge_policy=1 --metadata_read_fault_one_in=0 --metadata_write_fault_one_in=0 --min_blob_size=16 --min_write_buffer_number_to_merge=2 --mmap_read=0 --mock_direct_io=False --nooverwritepercent=1 --num_file_reads_for_auto_readahead=0 --open_files=-1 --open_metadata_read_fault_one_in=0 --open_metadata_write_fault_one_in=0 --open_read_fault_one_in=0 --open_write_fault_one_in=0 --ops_per_thread=20000000 --optimize_filters_for_hits=1 --optimize_filters_for_memory=0 --optimize_multiget_for_io=1 --paranoid_file_checks=1 --partition_filters=0 --partition_pinning=1 --pause_background_one_in=10000 --periodic_compaction_seconds=10 --prefix_size=8 --prefixpercent=0 --prepopulate_blob_cache=1 --prepopulate_block_cache=1 --preserve_internal_time_seconds=0 --progress_reports=0 --promote_l0_one_in=0 --read_amp_bytes_per_bit=0 --read_fault_one_in=0 --readahead_size=524288 --readpercent=60 --recycle_log_file_num=1 --reopen=20 --report_bg_io_stats=0 --reset_stats_one_in=1000000 --sample_for_compression=5 --secondary_cache_fault_one_in=0 --secondary_cache_uri= --skip_stats_update_on_db_open=1 --snapshot_hold_ops=100000 --soft_pending_compaction_bytes_limit=68719476736 --sqfc_name=foo --sqfc_version=1 --sst_file_manager_bytes_per_sec=0 --sst_file_manager_bytes_per_truncate=0 --stats_dump_period_sec=10 --stats_history_buffer_size=1048576 --strict_bytes_per_sync=1 --subcompactions=2 --sync=0 --sync_fault_injection=0 --table_cache_numshardbits=0 --target_file_size_base=16777216 --target_file_size_multiplier=1 --test_batches_snapshots=0 --top_level_index_pinning=3 --uncache_aggressiveness=118 --universal_max_read_amp=-1 --unpartitioned_pinning=0 --use_adaptive_mutex=0 --use_adaptive_mutex_lru=1 --use_attribute_group=0 --use_blob_cache=0 --use_delta_encoding=1 --use_direct_io_for_flush_and_compaction=0 --use_direct_reads=0 --use_full_merge_v1=0 --use_get_entity=0 --use_merge=0 --use_multi_cf_iterator=0 --use_multi_get_entity=0 --use_multiget=1 --use_put_entity_one_in=0 --use_shared_block_and_blob_cache=1 --use_sqfc_for_range_queries=1 --use_timed_put_one_in=0 --use_write_buffer_manager=0 --user_timestamp_size=0 --value_size_mult=32 --verification_only=0 --verify_checksum=1 --verify_checksum_one_in=1000000 --verify_compression=0 --verify_db_one_in=10000 --verify_file_checksums_one_in=1000000 --verify_iterator_with_expected_state_one_in=5 --verify_sst_unique_id_in_manifest=1 --wal_bytes_per_sync=0 --wal_compression=none --write_buffer_size=33554432 --write_dbid_to_manifest=0 --write_fault_one_in=0 --writepercent=35
```

Reviewed By: cbi42

Differential Revision: D60890580

Pulled By: hx235

fbshipit-source-id: 401f90d6d351c7ee11088cad06fb00e54062d416
2024-08-09 14:51:36 -07:00
Hui Xiao 408e8d4c85 Handle injected write error after successful WAL write in crash test + misc (#12838)
Summary:
**Context/Summary:**
We discovered the following false positive in our crash test lately:
(1) PUT() writes k/v to WAL but fails in `ApplyWALToManifest()`. The k/v is in the WAL
(2) Current stress test logic will rollback the expected state of such k/v since PUT() fails
(3) If the DB crashes before recovery finishes and reopens, the WAL will be replayed and the k/v is in the DB while the expected state have been roll-backed.

We decided to leave those expected state to be pending until the loop-write of the same key succeeds.

Bonus: Now that I realized write to manifest can also fail the write which faces the similar problem as https://github.com/facebook/rocksdb/pull/12797, I decided to disable fault injection on user write per thread (instead of globally) when tracing is needed for prefix recovery; some refactory

Pull Request resolved: https://github.com/facebook/rocksdb/pull/12838

Test Plan:
Rehearsal CI
Run below command (varies on sync_fault_injection=1,0 to verify ExpectedState behavior) for a while to ensure crash recovery validation works fine

```
python3 tools/db_crashtest.py --simple blackbox --interval=30 --WAL_size_limit_MB=0 --WAL_ttl_seconds=0 --acquire_snapshot_one_in=10000 --adaptive_readahead=1 --adm_policy=1 --advise_random_on_open=0 --allow_concurrent_memtable_write=0 --allow_data_in_errors=True --allow_fallocate=0 --async_io=0 --auto_readahead_size=0 --avoid_flush_during_recovery=0 --avoid_flush_during_shutdown=0 --avoid_unnecessary_blocking_io=0 --backup_max_size=104857600 --backup_one_in=0 --batch_protection_bytes_per_key=0 --bgerror_resume_retry_interval=1000000 --block_align=1 --block_protection_bytes_per_key=4 --block_size=16384 --bloom_before_level=4 --bloom_bits=56.810257702625165 --bottommost_compression_type=none --bottommost_file_compaction_delay=0 --bytes_per_sync=262144 --cache_index_and_filter_blocks=1 --cache_index_and_filter_blocks_with_high_priority=1 --cache_size=8388608 --cache_type=auto_hyper_clock_cache --charge_compression_dictionary_building_buffer=1 --charge_file_metadata=1 --charge_filter_construction=1 --charge_table_reader=0 --check_multiget_consistency=0 --check_multiget_entity_consistency=1 --checkpoint_one_in=10000 --checksum_type=kxxHash --clear_column_family_one_in=0 --column_families=1 --compact_files_one_in=1000 --compact_range_one_in=1000 --compaction_pri=4 --compaction_readahead_size=1048576 --compaction_ttl=10 --compress_format_version=1 --compressed_secondary_cache_ratio=0.0 --compressed_secondary_cache_size=0 --compression_checksum=0 --compression_max_dict_buffer_bytes=0 --compression_max_dict_bytes=0 --compression_parallel_threads=1 --compression_type=none --compression_use_zstd_dict_trainer=0 --compression_zstd_max_train_bytes=0 --continuous_verification_interval=0 --daily_offpeak_time_utc=04:00-08:00 --data_block_index_type=1 --db_write_buffer_size=0 --default_temperature=kWarm --default_write_temperature=kCold --delete_obsolete_files_period_micros=30000000 --delpercent=20 --delrangepercent=20 --destroy_db_initially=0 --detect_filter_construct_corruption=0 --disable_file_deletions_one_in=10000 --disable_manual_compaction_one_in=1000000 --disable_wal=0 --dump_malloc_stats=0 --enable_checksum_handoff=1 --enable_compaction_filter=0 --enable_custom_split_merge=0 --enable_do_not_compress_roles=0 --enable_index_compression=1 --enable_memtable_insert_with_hint_prefix_extractor=0 --enable_pipelined_write=0 --enable_sst_partitioner_factory=0 --enable_thread_tracking=0 --enable_write_thread_adaptive_yield=0 --error_recovery_with_no_fault_injection=1 --exclude_wal_from_write_fault_injection=0 --fail_if_options_file_error=1 --fifo_allow_compaction=0 --file_checksum_impl=crc32c --fill_cache=1 --flush_one_in=1000000 --format_version=3 --get_all_column_family_metadata_one_in=1000000 --get_current_wal_file_one_in=0 --get_live_files_apis_one_in=1000000 --get_properties_of_all_tables_one_in=1000000 --get_property_one_in=100000 --get_sorted_wal_files_one_in=0 --hard_pending_compaction_bytes_limit=274877906944 --high_pri_pool_ratio=0.5 --index_block_restart_interval=4 --index_shortening=2 --index_type=0 --ingest_external_file_one_in=0 --initial_auto_readahead_size=16384 --inplace_update_support=0 --iterpercent=10 --key_len_percent_dist=1,30,69 --key_may_exist_one_in=100 --last_level_temperature=kWarm --level_compaction_dynamic_level_bytes=1 --lock_wal_one_in=10000 --log_file_time_to_roll=60 --log_readahead_size=16777216 --long_running_snapshots=1 --low_pri_pool_ratio=0 --lowest_used_cache_tier=0 --manifest_preallocation_size=0 --manual_wal_flush_one_in=0 --mark_for_compaction_one_file_in=10 --max_auto_readahead_size=16384 --max_background_compactions=1 --max_bytes_for_level_base=67108864 --max_key=100000 --max_key_len=3 --max_log_file_size=1048576 --max_manifest_file_size=32768 --max_sequential_skip_in_iterations=1 --max_total_wal_size=0 --max_write_batch_group_size_bytes=16 --max_write_buffer_number=10 --max_write_buffer_size_to_maintain=8388608 --memtable_insert_hint_per_batch=1 --memtable_max_range_deletions=0 --memtable_prefix_bloom_size_ratio=0.01 --memtable_protection_bytes_per_key=1 --memtable_whole_key_filtering=1 --memtablerep=skip_list --metadata_charge_policy=1 --metadata_read_fault_one_in=0 --metadata_write_fault_one_in=8 --min_write_buffer_number_to_merge=1 --mmap_read=1 --mock_direct_io=False --nooverwritepercent=1 --num_file_reads_for_auto_readahead=1 --open_files=-1 --open_metadata_read_fault_one_in=0 --open_metadata_write_fault_one_in=8 --open_read_fault_one_in=0 --open_write_fault_one_in=8 --ops_per_thread=100000000 --optimize_filters_for_hits=1 --optimize_filters_for_memory=1 --optimize_multiget_for_io=1 --paranoid_file_checks=0 --partition_filters=0 --partition_pinning=3 --pause_background_one_in=1000000 --periodic_compaction_seconds=2 --prefix_size=7 --prefixpercent=0 --prepopulate_block_cache=0 --preserve_internal_time_seconds=0 --progress_reports=0 --promote_l0_one_in=0 --read_amp_bytes_per_bit=0 --read_fault_one_in=1000 --readahead_size=524288 --readpercent=10 --recycle_log_file_num=1 --reopen=0 --report_bg_io_stats=0 --reset_stats_one_in=1000000 --sample_for_compression=0 --secondary_cache_fault_one_in=0 --set_options_one_in=0 --skip_stats_update_on_db_open=1 --snapshot_hold_ops=100000 --soft_pending_compaction_bytes_limit=68719476736 --sqfc_name=foo --sqfc_version=0 --sst_file_manager_bytes_per_sec=104857600 --sst_file_manager_bytes_per_truncate=0 --stats_dump_period_sec=10 --stats_history_buffer_size=0 --strict_bytes_per_sync=1 --subcompactions=4 --sync=1 --sync_fault_injection=0 --table_cache_numshardbits=6 --target_file_size_base=16777216 --target_file_size_multiplier=1 --test_batches_snapshots=0 --top_level_index_pinning=2 --uncache_aggressiveness=239 --universal_max_read_amp=-1 --unpartitioned_pinning=1 --use_adaptive_mutex=1 --use_adaptive_mutex_lru=1 --use_attribute_group=0 --use_delta_encoding=0 --use_direct_io_for_flush_and_compaction=0 --use_direct_reads=0 --use_full_merge_v1=0 --use_get_entity=0 --use_merge=0 --use_multi_cf_iterator=0 --use_multi_get_entity=0 --use_multiget=0 --use_put_entity_one_in=0 --use_sqfc_for_range_queries=1 --use_timed_put_one_in=0 --use_write_buffer_manager=0 --user_timestamp_size=0 --value_size_mult=32 --verification_only=0 --verify_checksum=1 --verify_checksum_one_in=1000000 --verify_compression=0 --verify_db_one_in=100000 --verify_file_checksums_one_in=1000000 --verify_iterator_with_expected_state_one_in=5 --verify_sst_unique_id_in_manifest=1 --wal_bytes_per_sync=0 --wal_compression=none --write_buffer_size=33554432 --write_dbid_to_manifest=0 --write_fault_one_in=8 --writepercent=40
```

Reviewed By: cbi42

Differential Revision: D59377075

Pulled By: hx235

fbshipit-source-id: 91f602fd67e2d339d378cd28b982095fd073dcb6
2024-07-29 13:51:49 -07:00
Hui Xiao 7263f51d50 Improve comment of ExpectedValue in db stress (#11456)
Summary:
**Context/Summary:**
https://github.com/facebook/rocksdb/pull/11424 made me realize there are a couple gaps in my `ExpectedValue` comments so I updated them, along with separating `ExpectedValue` into separate files so it's clearer that `ExpectedValue` can be used without updating `ExpectedState` (e.g, TestMultiGet() where we care about value base of expected value but not updating the ExpectedState).

Pull Request resolved: https://github.com/facebook/rocksdb/pull/11456

Test Plan: CI

Reviewed By: jowlyzhang

Differential Revision: D45965070

Pulled By: hx235

fbshipit-source-id: dcee690c13b00a3119757ea9d43b646f9644e1a9
2023-05-18 09:44:15 -07:00